Communication system, base station apparatus, mobile station apparatus, and communication method

ABSTRACT

A communication system comprises at least a base station device and a terminal device. The terminal device transmits a demodulation reference signal associated with a physical channel, receives a configuration of comb of the demodulation reference signal, and transmits the demodulation reference signal mapped based on the configuration of comb. The base station device transmits a configuration of comb of a demodulation reference signal related to a physical channel.

RELATED APPLICATION

This application is a Continuation of copending application Ser. No.14/130,666 filed on Jan. 2, 2014, which is the National Phase ofPCT/JP2012/066896 filed Jul. 2, 2012, and which claims priority toApplication No. 2011-148043 filed in Japan on Jul. 4, 2011. The entirecontents of all of the above applications is hereby incorporated byreference.

TECHNICAL FIELD

The present invention relates to a communication system, a base stationapparatus, a mobile station apparatus and a communication method.

BACKGROUND ART

3GPP (3rd Generation Partnership Project) is a project that is intendedto study and formulate specifications of a mobile communication systembased on a network that is upgraded from W-CDMA (Wideband-Code DivisionMultiple Access) and GSM (registered trademark) (Global System forMobile Communications). Currently being studied under 3GPP, with theadvance of the third-generation radio access technology (hereinafterreferred to as “LTE (Long Term Evolution)” or “EUTRA (Evolved UniversalTerrestrial Radio Access)” and the use of a wider frequency bandwidth,is a mobile communication system (hereinafter referred to as “LTE-A(Long Term Evolution-Advanced)” or “Advanced-EUTRA”) that permits evenhigher data transmission and reception.

As a communication scheme in LTE, 3GPP is studying, for a downlink,OFDMA (Orthogonal Frequency Division Multiple Access) that performsuser-multiplexing using mutually orthogonal subcarriers and SC-FDMA(Single Carrier-Frequency Division Multiple Access) for an uplink.

As a communication scheme in LTE-A, 3GPP is studying OFDMA for thedownlink and for the uplink, an introduction of Clustered-SC-FDMA(Clustered-Single Carrier-Frequency Division Multiple Access, alsoreferred to as DFT-s-OFDM with Spectrum Division Control or DFT-precodedOFDM) in addition to SC-FDMA.

In a radio communication system, a communication area may be expanded byintroducing a cellular structure to arrange in a cell-like fashion aplurality of coverage areas covered by base station apparatus. Althougheven a mobile station apparatus in a cell edge (cell end) regioncommunicates without being interfered by using different frequenciesbetween adjacent cells (sectors), frequency usage efficiency isproblematic. In LTE, the frequency usage efficiency is substantiallyincreased by using the same frequency repeatedly in each of the cells(sectors). However, a mobile station apparatus in the cell edge regionis likely to be affected by interference from an adjacent cell, andcommunication quality is degraded. This entails reducing or suppressinginterference to the mobile station apparatus in the cell edge region.

Currently being studied in LTE-A as a method of reducing or suppressinginterference to the mobile station apparatus in the cell edge region isa Coordinated Multi-Point Transmission/Reception (COMP) that performsinterference coordination to cause adjacent cells (adjacent transmissionand reception points) to coordinate each other. The word point hereinrefers to a transmission point (transmission station apparatus) of asignal and a reception point (reception station apparatus) of a signal.For example, the point may be a base station apparatus. Also, the pointmay be a mobile station apparatus. Also, the point may be a relaystation apparatus. The point may be RRH (Remote Radio Head) as anupgraded antenna facility.

In coordinated communications, orthogonal resources alone of a uplinkdemodulation reference signal (DMRS: Demodulation Reference Signal) ofLTE are insufficient to ensure orthogonality between the cells(transmission and reception points). Currently being studied is anincrease in the orthogonal resources of DMRS that may be achieved bychanging the frequency resource allocation of DMRS in a frequencyspectrum from localized resource allocation to distributed resourceallocation (for example, comb spectrum arrangement at two-subcarrierintervals such as a sounding reference signal (SRS: Sounding ReferenceSignal) (Non Patent Literature 1).

Disclosed further in the coordinated communications are a scenario wherecell IDs (physical layer cell identities) different among a plurality ofpoints are set, and a scenario where a common cell ID is set (Non PatentLiterature 2).

CITATION LIST Non Patent Literature

-   NPL 1: “UL-CoMP Rel-11 Proposed Enhancements”, 3GPP TSG RAN WG1    Meeting #65, R1-111477, May 9-13, 2011.

NPL 2: “On Simulations Assumptions for Phase 2 CoMP Evaluations,” 3GPPTSG RAN WG1 Meeting #64, R1-110650, Feb. 21-25, 2011.

SUMMARY OF INVENTION Technical Problem

However, since interference coordination is not performed betweenuncoordinated adjacent cells (points), it is difficult to avoidinterference between the uncoordinated adjacent cells (points).

The present invention has been developed in view of the above problem.It is an object of the present invention to provide a communicationsystem, a base station apparatus, a mobile station apparatus, and acommunication method for reducing interference between uncoordinatedadjacent cells.

Solution to Problem

(1) To achieve the object, the present invention comprises acommunication system as described below. The communication systemcomprises a base station apparatus and a mobile station apparatus. Thebase station apparatus notifies the mobile station apparatus of adownlink control information format. The downlink control informationformat comprises resource allocation information that indicatesswitching of resource allocation for an uplink demodulation referencesignal between localized resource allocation and distributed resourceallocation, and information on a frequency offset of the distributedresource allocation for the uplink demodulation reference signalspecific to the mobile station apparatus. The mobile station apparatusdetermines the resource allocation for the uplink demodulation referencesignal based on the frequency offset of the mobile station apparatus ina case in which information included in the downlink control informationformat indicates that the distributed resource allocation is enabledbased on the resource allocation information in accordance with acertain information comprised in the downlink control informationformat, and transmits the uplink demodulation reference signal to thebase station apparatus.

(2) In the communication system of the present invention in view of thecommunication system (1), the base station apparatus notifies the mobilestation apparatus of the downlink control information format comprisinginformation indicating a availability of frequency offset hopping of thedistributed resource allocation for the uplink demodulation referencesignal. The mobile station apparatus determines the resource allocationfor the uplink demodulation reference signal based on a frequency offsethopping pattern specific to a cell determined in response to a slotnumber and the frequency offset specific to the mobile stationapparatus, in a case in which information comprised in the downlinkcontrol information format indicates that the distributed resourceallocation is enabled based on the resource allocation information andindicates that the frequency offset hopping of the distributed resourceallocation is enabled.

(3) In the communication system of the present invention in view of thecommunication system (2), the frequency offset hopping pattern specificto the cell is configured based on a pseudo-random sequencecorresponding to the slot number.

(4) In the communication system of the present invention in view of thecommunication system (3), an initial value of the pseudo-random sequenceis configured on the basis of a physical layer cell identity.

(5) In the communication system of the present invention in view of thecommunication system (3), the initial value of the pseudo-randomsequence is configured on the basis of a virtual cell identity.

(6) A communication system of the present invention comprises a basestation apparatus and a mobile station apparatus. The base stationapparatus notifies the mobile station apparatus of a downlink controlinformation format. The downlink control information format comprisesresource allocation information for an uplink demodulation referencesignal, a frequency offset for the uplink demodulation reference signalspecific to the mobile station apparatus, and a frequency offset shiftpattern for the uplink demodulation reference signal specific to a cell.The mobile station apparatus determines resource allocation for theuplink demodulation reference signal using the frequency offset specificto the mobile station apparatus, the frequency offset shift patternspecific to the cell, and a slot number, in a case in which informationcomprised in the downlink control information format indicatesdistributed resource allocation is enabled based on the resourceallocation information. The mobile station apparatus then transmits theuplink demodulation reference signal to the base station apparatus.

(7) In the communication system of the present invention in view of thecommunication system (6), the frequency offset shift pattern specific tothe cell is configured on the basis of a physical layer cell identity.

(8) In the communication system of the present invention in view of thecommunication system (6), the frequency offset shift pattern specific tothe cell is configured on the basis of a virtual cell identity.

(9) A base station apparatus of the present invention is incommunication with a mobile station apparatus. The base stationapparatus comprises a transmitter configured to notify the mobilestation apparatus of a downlink control information format, the downlinkcontrol information format comprising resource allocation informationthat indicates switching of resource allocation of an uplinkdemodulation reference signal between localized resource allocation anddistributed resource allocation, and a frequency offset of thedistributed resource allocation of the uplink demodulation referencesignal specific to the mobile station apparatus, and a receiverconfigured to receive the uplink demodulation reference signal based onthe resource allocation indicated by the resource allocationinformation.

(10) The base station apparatus of the present invention is in view ofthe base station apparatus (9), wherein the receiver is configured tonotify the mobile station apparatus of the downlink control informationformat that comprises information indicating a availability of frequencyoffset hopping of the distributed resource allocation for the uplinkdemodulation reference signal.

(11) A base station apparatus of the present invention is incommunication with a mobile station apparatus. The base stationapparatus comprises a transmitter configured to notify the mobilestation apparatus of a downlink control information format, the downlinkcontrol information format comprising resource allocation informationfor an uplink demodulation reference signal, a frequency offset for theuplink demodulation reference signal specific to the mobile stationapparatus, and a frequency offset shift pattern for the uplinkdemodulation reference signal specific to a cell.

(12) A mobile station apparatus of the present invention is incommunication with a base station apparatus. The mobile stationcomprises a receiver configured to receive a downlink controlinformation format, means that determines resource allocation of anuplink demodulation reference signal in accordance with a frequencyoffset specific to the mobile station apparatus, in a case in whichinformation comprised in the downlink control information formatdictates distributed resource allocation in resource allocationinformation for the uplink demodulation reference signal, and atransmitter configured to transmit the uplink demodulation referencesignal to the base station apparatus.

(13) The mobile station apparatus of the present invention is in view ofthe mobile station (12), wherein the transmitter is configured todetermine the resource allocation for the uplink demodulation referencesignal on the basis of a frequency offset hopping pattern specific to acell determined in response to a slot number and the frequency offsetfor the uplink demodulation reference signal specific to the mobilestation apparatus, in a case in which information, comprised in thedownlink control information format and concerning a availability offrequency offset hopping of the distributed resource allocation for theuplink demodulation reference signal, indicates that the frequencyoffset hopping is enabled.

(14) A mobile station apparatus of the present invention is incommunication with a base station apparatus. The mobile stationapparatus comprises a receiver configured to receive a downlink controlinformation format, and a transmitter configured to determine resourceallocation for an uplink demodulation reference signal using a frequencyoffset specific to the mobile station apparatus, a frequency offsetshift pattern specific to a cell, and a slot number, in a case in whichinformation comprised in the downlink control information formatindicates that the distributed resource allocation is enabled based onresource allocation information.

(15) A communication method of the present invention of a communicationsystem comprising a base station apparatus and a mobile stationapparatus, comprises at least, a step of the base station apparatus ofnotifying the mobile station apparatus of a downlink control informationformat, the downlink control information format comprising resourceallocation information that dictates switching of resource allocationfor an uplink demodulation reference signal between localized resourceallocation and distributed resource allocation, and a frequency offsetof the distributed resource allocation for the uplink demodulationreference signal specific to the mobile station apparatus, and a step ofthe mobile station apparatus of determining the resource allocation forthe uplink demodulation reference signal on the basis of the frequencyoffset of the mobile station apparatus in a case in which informationcomprised in the downlink control information format indicates that thedistributed resource allocation is enabled based on the resourceallocation information, and a step of the mobile station apparatus oftransmitting the uplink demodulation reference signal to the basestation apparatus.

(16) The communication method of the present invention in view of thecommunication method (15), comprises at least, a step of the basestation apparatus of notifying the mobile station apparatus of thedownlink control information format comprising information indicating aavailability of frequency offset hopping of the distributed resourceallocation for the uplink demodulation reference signal, and a step ofthe mobile station apparatus of determining the resource allocation forthe uplink demodulation reference signal using a frequency offsethopping pattern specific to a cell determined in response to a slotnumber and a frequency offset specific to the mobile station apparatus,in a case in which the information comprised in the downlink controlinformation format indicates that the distributed resource allocation isenabled based on the resource allocation information and indicates thatthe frequency offset hopping of the distributed resource allocation isenabled.

(17) A communication method of the present invention of a communicationsystem comprising a base station apparatus and a mobile stationapparatus, comprises at least, a step of the base station apparatus ofnotifying the mobile station apparatus of a downlink control informationformat, the downlink control information format comprising resourceallocation information for an uplink demodulation reference signal, afrequency offset for the uplink demodulation reference signal specificto the mobile station apparatus, and a frequency offset shift patternfor the uplink demodulation reference signal specific to a cell, and astep of the mobile station apparatus of determining the resourceallocation for the uplink demodulation reference signal using thefrequency offset specific to the mobile station apparatus, the frequencyoffset shift pattern specific to the cell, and a slot number in a casein which information comprised in the downlink control informationformat indicates that distributed resource allocation is enabled basedon the resource allocation information, and a step of the mobile stationapparatus of transmitting the uplink demodulation reference signal tothe base station apparatus.

The communication system, the base station apparatus, the mobile stationapparatus and the communication method thus reduce interference betweenuncoordinated adjacent cells (points).

Advantageous Effects of Invention

According to the present invention, interference between adjacent cellsis reduced.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a configuration example of a channel in an embodimentof the present invention.

FIG. 2 is a block diagram schematically illustrating a configuration ofa base station apparatus 100 of the embodiment of the present invention.

FIG. 3 is a block diagram schematically illustrating a configuration ofa mobile station apparatus 200 of the embodiment of the presentinvention.

FIG. 4A illustrates a configuration example of DMRS resource allocationof a first embodiment of the present invention.

FIG. 4B illustrates a configuration example of the DMRS resourceallocation of the first embodiment of the present invention.

FIG. 5 illustrates an example of DMRS distributed resource allocation ofthe first embodiment of the present invention.

FIG. 6 is a block diagram schematically illustrating a configuration ofa scheduling unit 204 of the mobile station apparatus 200 of the firstembodiment of the present invention.

FIG. 7A illustrates a configuration example of a control informationfield comprised in a DCI format.

FIG. 7B illustrates a configuration example of the control informationfield comprised in the DCI format.

FIG. 7C illustrates a configuration example of the control informationfield comprised in the DCI format.

FIG. 8A illustrates an example of frequency offset hopping of the DMRSof the first embodiment of the present invention.

FIG. 8B illustrates an example of the frequency offset hopping of theDMRS of the first embodiment of the present invention.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention are described with reference to thedrawings. FIG. 1 illustrates a configuration example of a channel in anembodiment of the present invention. Physical downlink channels are aphysical downlink control channel (PDCCH) and a physical downlink sharedchannel (PDSCH). Physical uplink channels are a physical uplink sharedchannel (PUSCH) and a physical uplink control channel (PUCCH).

A base station apparatus 100 transmits to a mobile station apparatus 200a downlink reference signal (DRS, also referred to as a downlink pilotsignal or a downlink pilot channel). The mobile station apparatus 200transmits to the base station apparatus 100 an uplink reference signal(URS, also referred to as an uplink pilot signal or an uplink pilotchannel). Two types of the uplink reference signals are supported. Onetype is a demodulation reference signal (DMRS) that the base stationapparatus 100 uses to perform demodulation of data/informationtransmitted using PUCCH and/or PUSCH. Another type is a soundingreference signal (SRS) that the base station apparatus 100 uses toestimate a channel state of an uplink.

The PDCCH is a physical channel that is used to notify the mobilestation apparatus of downlink control information (DCI) (to specify theDCI to the mobile station). The DCIs are information on resourceallocation for the PDSCH, information on HARQ process related todownlink data, and information on resource allocation for the PUSCH andthe like. The PDCCH is transmitted on an aggregation of one or morecontrol channel elements (CCE). By detecting the PDCCH comprising theone or more CCEs, the mobile station apparatus 200 performs reception ofscheduling assignments and other control information transmitted usingthe PDCCH from the base station apparatus 100. The base stationapparatus 100 maps the CCE to a plurality of resource element groups(REG, also referred to as mini-CCE) that are distributed in terms offrequency and time domain. The resource element herein refers to a unitresource having one OFDM symbol (time domain) and one subcarrier(frequency domain).

A plurality of formats is defined in accordance with the downlinkcontrol information transmitted in PDCCH. The format of the downlinkcontrol information is hereinafter also referred to as a DCI format.

DCI formats 1/1A/2 are defined as the DCI formats for the downlink. TheDCI formats 1/1A are used to perform transmission in the PDSCH intransmit diversity using one or more transmit antenna ports. Also theDCI format 2 is used to perform transmission in the PDSCH using spatialmultiplexing (SM) based on multiple input multiple output (MIMO). As theDCI format, a plurality of DCI formats having the same bit size or aplurality of DCI formats having different bit sizes may be defined.There are a plurality of the DCI formats consisting of the same bit sizeand/or different bit size.

DCI format 0 and DCI format 4 are defined as the DCI formats for theuplink. The DCI format 0 is used to schedule transmission in the PUSCHon a single transmit port. The DCI format 4 is used to scheduletransmission in the PUSCH using the SM based on the MIMO.

The base station apparatus 100 scrambles a CRC (cyclic redundancy check)code by a RNTI (Radio Network Temporary Identifier) with a DCI formatand transmits one or more DCIS in the PDCCH with the DCI format and withthe CRC to the mobile station apparatus 200. The mobile stationapparatus 200 changes an interpretation of the DCI transmitted using theDCI format on the basis of which RNTI the cyclic redundancy check codeis scrambled. For example, if the cyclic redundancy check code isscrambled by C-RNTI (Cell-Radio Network Temporary Identifier) that isassigned by the base station apparatus 100, the mobile station apparatus200 determines that that the DCI has been addressed to the mobilestation apparatus 200.

The PDCCH is coded on a per DCI format basis. In other words, the mobilestation apparatus 200 detects a plurality of PDCCHs, thereby acquiringinformation on a resource allocation for the downlink, information on aresource allocation for the uplink, and other control information. EachPDCCH is accompanied by a value of CRC (cyclic redundancy check) thatpermits the format of the PDCCH to be identified, and the mobile stationapparatus 200 performs the CRC on each set of CCE that may form thePDCCH. The mobile station apparatus 200 acquires a successfullyCRC-checked PDCCH as a PDCCH addressed thereto. This is also referred toas blind decoding. A space of the set of CCE that may form the PDCCH onwhich the mobile station apparatus 200 performs blind decoding isreferred to as a search area (Search Space). More specifically, themobile station apparatus 200 performs blinding decoding on the CCEwithin the search space, and detects a PDCCH addressed thereto.

If the resource allocation for the PDSCH is transmitted using the PDCCHto the mobile station apparatus 200, the mobile station apparatus 200receives at least one of the downlink signals (downlink data (transportblock for downlink shared channel (DL-SCH)) and downlink control data(downlink control information) and a downlink reference signal (DRS)) onthe basis of the PDSCH in response to the resource allocation indicatedby the PDCCH from the base station apparatus 100. More specifically, thePDCCH comprising the resource allocation of the PDSCH may also bereferred to as a signal for assigning a resource to the downlink(hereinafter referred to as a “downlink transmission permit signal” or“downlink grant”).

If the resource allocation for the PUSCH is transmitted using the PDCCHto the mobile station apparatus 200, the mobile station apparatus 200transmits at least one of the uplink signals (uplink data (transportblock for uplink shared channel (UL-SCH)), uplink control data (uplinkcontrol information) and an uplink reference signal (URS)) on the PUSCHregion corresponding to information on the resource allocationtransmitted using the PDCCH from the base station apparatus 100. Morespecifically, the PDCCH may also be referred to as a signal forpermitting data transmission in the uplink (hereinafter referred to as a“uplink transmission permit signal” or “uplink grant”).

The PDSCH is a physical channel that is used to transmit the downlinkdata (transport block for the downlink shared channel (DL-SCH)) orpaging information (transport block for a paging channel (PCH)). Usingthe PDSCH assigned by the PDCCH, the base station apparatus 100transmits the downlink data (transport block for the downlink sharedchannel (DL-SCH)) to the mobile station apparatus 200.

The downlink data refers to user data, for example, and DL-SCH is atransport channel. DL-SCH is characterized by support for HARQ, supportfor dynamic link adaptation, possibility to use beamforming and supportfor both dynamic and semi-static resource allocation etc.

The PUSCH is a physical channel that is used to mainly transmit theuplink data (transport block for the uplink shared channel (UL-SCH)).Using the PUSCH assigned by the PDCCH transmitted from the base stationapparatus 100, the mobile station apparatus 200 transmits to the basestation apparatus 100 the uplink data (transport block for the uplinkshared channel (UL-SCH)). If the base station apparatus 100 hasperformed a PUSCH scheduling operation on the mobile station apparatus200, the mobile station apparatus 200 also transmits the uplink controlsignal (UCI) using the PUSCH.

The uplink data refers to user data, for example, and UL-SCH is atransport channel. The PUSCH is a physical channel that is defined(constructed) by the time domain and the frequency domain. UL-SCH ischaracterized by possibility to use beamforming, support for dynamiclink adaptation, support for HARQ and support for both dynamic andsemi-static resource allocation.

The uplink data (UL-SCH) and the downlink data (DL-SCH) may comprise aradio resource control signal (hereinafter referred to as “RRC”) that isone of the signals from a higher layer to be exchanged between the basestation apparatus 100 and the mobile station apparatus 200. The uplinkdata (UL-SCH) and the downlink data (DL-SCH) may comprise an MAC (MediumAccess Control) control element to be exchanged between the base stationapparatus 100 and the mobile station apparatus 200.

The base station apparatus 100 and the mobile station apparatus 200transmit and receive RRC signaling by a higher layer (Radio ResourceControl Layer). The base station apparatus 100 and the mobile stationapparatus 200 also transmit and receive the MAC control element by ahigher layer (MAC (Medium Access Control) layer).

The PUCCH is a channel that is used to transmit uplink controlinformation (UCI). The uplink control information comprises channelstate information (CSI), channel quality information (CQI), precodingmatrix indicator (PMI), and rank indicator (RI). The uplink controlinformation further comprises information indicating ACK/NACK in theHARQ for the downlink transport block. The uplink control informationfurther comprises a scheduling request by which the mobile stationapparatus 200 requests the resource allocation to transmit the uplinkdata (requests transmission in the UL-SCH).

In a case in which an initial access is performed, the mobile stationapparatus 200 may estimate a Physical-layer Cell Identity (PCI) using aphysical-layer identity group and a physical-layer cell identity,obtained from a Primary Synchronization Signal (PSS) for use in timesynchronization, and a Secondary Synchronization Signal (SSS) for use incell synchronization and frame timing synchronization. If a connectionis established between the base station apparatus 100 and the mobilestation apparatus 200, the base station apparatus 100 may notify themobile station apparatus 200 of the physical-layer cell identity usingRRC signaling. The RRC signaling may also be referred to as higher layersignaling.

In LTE/LTE-A, a signal sequence is assigned to each physical channel toreduce intra-cell/inter-cell interference. If mobile station apparatusesbelonging to different cells remain in the same signal sequence (betweenslots), a transmission signal from the mobile station apparatus 200belonging to an adjacent cell becomes interference to the base stationapparatus 100. To prevent the signal sequence from continuouslyremaining the same from slot to slot between the mobile stationapparatuses (having physical layer cell identities different from cellto cell), Sequence Group Hopping (SGH) and Sequence Hopping (SH) areused so that inter-cell interference is randomized. The inter-cellinterference is randomized by configuring the initial value of a signalsequence generator on the basis of a physical layer cell identity.

The inter-cell interference is further randomized by using cyclichopping that applies a cyclic shift different from slot to slot.

For DMRS, a reference signal sequence is generated using an orthogonalcover code (OCC). In accordance with the present invention, theorthogonal cover codes [w^((λ))(0), w^((λ))(1)] comprise two codes [+1,+1] and [+1, −1]. The mobile station apparatus 200 performs a spreadprocess using an orthogonal cover code for two DMRS symbols with respectto the PUSCH assigned to one subframe, thereby generating an uplinkreference signal sequence. If the PUSCH and the DMRS resource for thePUSCH are transmitted on the same frequency domain from different mobilestation apparatus 200, the base station apparatus 100 may perform achannel estimation for the DMRS transmitted from the different mobilestation apparatuses 200 by performing a despread process on theorthogonal cover code from the received DMRS symbol. If the DMRSs havingdifferent sequence lengths (different bandwidths) overlap each other,the spread process by the orthogonal cover code is performed on the twoDMRS symbols for the PUSCH. The mobile station apparatus 200 thusdemultiplexes the plurality of DMRSs transmitted from the differentmobile station apparatuses 200. Even if DMRSs different in sequencelength are multiplexed at the same timing and in the same transmissionfrequency band, orthogonality is ensured. Here, λ represents a transmitport.

In the DMRS and the PUCCH, the cyclic shift (phase shift amount that isto be multiplied by each subcarrier) is determined on a per slot basisand on a per symbol basis using a pseudo-random sequence. An amount ofcyclic shift is randomized by changing the cyclic shift amount in arandom fashion. This arrangement controls cyclic shifting so that thesame cyclic shift is not continuously set in the different mobilestation apparatuses (this is herein called cyclic shift hopping). Morespecifically, in the cyclic shift hopping, interference between themobile station apparatuses belonging to the different cells is reducedby randomizing the cyclic shifts in the mobile station apparatusesbelonging to the different cells.

In the SRS, the distributed resource allocation of comb spectra isintroduced. In this way, the channel estimation of the same transmissionfrequency band is performed on the mobile station apparatus 200 having adifference transmission bandwidth (different consequence length). Morespecifically, the base station apparatus 100 performs to the mobilestation apparatus 200 not only code multiplexing by the same bandwidthand the same time but also frequency multiplexing by different frequencyoffsets.

[Configuration of Base Station Apparatus 100]

FIG. 2 is a block diagram schematically illustrating a configuration ofthe base station apparatus 100 of the embodiment of the presentinvention. The base station apparatus 100 comprises a data control unit101, a transmission data modulator unit 102, a radio unit 103, ascheduling unit 104, a channel estimating unit 105, a reception datademodulator unit 106, a data extractor unit 107, a higher layer 108 andan antenna 109. The radio unit 103, the scheduling unit 104, the channelestimating unit 105, the reception data demodulator unit 106, the dataextractor unit 107, the higher layer 108 and the antenna 109 form areceiver (a base station receiver), and the data control unit 101, thetransmission data modulator unit 102, the radio unit 103, the schedulingunit 104, the higher layer 108 and the antenna 109 form a transmitter (abase station transmitter).

Processing of an uplink physical layer is performed by the antenna 109,the radio unit 103, the channel estimating unit 105, the reception datademodulator unit 106 and the data extractor unit 107. Processing of adownlink physical layer is performed by the antenna 109, the radio unit103, the transmission data modulator unit 102 and the data control unit101.

The data control unit 101 receives a transport channel from thescheduling unit 104. The data control unit 101 maps the transportchannel and a signal and a channel generated at a physical layer to thephysical channel in accordance with scheduling information input fromthe scheduling unit 104. Data thus mapped is output to the transmissiondata modulator unit 102.

The transmission data modulator unit 102 modulates transmission data inaccordance with an OFMD scheme. In accordance with the schedulinginformation from the scheduling unit 104 and a modulation scheme and acoding scheme corresponding to each PRB, the transmission data modulatorunit 102 performs signal processes on the data input from the datacontrol unit 101. The signal processes comprise data modulation,encoding, serial/parallel conversion of an input signal, IFFT (InverseFast Fourier Transform) operation, CP (Cyclic Prefix) insertion, andfiltering. The transmission data modulator unit 102 thus generatestransmission data and outputs the generated transmission data to theradio unit 103. The scheduling information comprises assignmentinformation on a downlink physical resource block (PRB: PhysicalResource Block), such as physical resource block location information offrequency and time. The modulation scheme and the coding schemecorresponding to each PRB may comprise information, such as modulationscheme: 16 QAM, and encoding ratio: 2/3 encoding rate.

The radio unit 103 up-converts modulation data input from thetransmission data modulator unit 102 into a radio signal, and thentransmits the up-radio signal to the mobile station apparatus 200 viathe antenna 109. The radio unit 103 also receives an uplink radio signalfrom the mobile station apparatus 200 via the antenna 109, anddown-converts the received signal into a baseband signal, and thenoutputs the baseband signal to the channel estimating unit 105 and thereception data demodulator unit 106.

The scheduling unit 104 performs a process in a medium access control(MAC) layer. The scheduling unit 104 performs mapping in a logicalchannel and a transport channel, and scheduling in the downlink and theuplink (comprising HARQ process, selection of a transport format, andthe like). In order to control processors of the physical layer in anintegral fashion, the scheduling unit 104 comprises an interface (notillustrated) between the scheduling unit 104 and each of the antenna109, the radio unit 103, the channel estimating unit 105, the receptiondata demodulator unit 106, the data control unit 101, the transmissiondata modulator unit 102 and the data extractor unit 107.

In accordance with uplink signals (CSI, CQI, PMI, RI, informationrepresenting ACK/NACK with respect to a downlink transport block, ascheduling request, a reference signal, and the like) received from themobile station apparatus 200, information of the PRB usable on eachmobile station apparatus 200, buffer status, scheduling informationinput from the higher layer 108, and the like, the scheduling unit 104generates scheduling information during the downlink scheduling for usein a selection process of the downlink transport format (a transmissionform, such as assignment of the physical resource block, the modulationscheme, and the encoding scheme) for modulating each piece of data, andfor use in retransmission control in HARQ and downlink. The schedulinginformation for use in the downlink scheduling is output to the datacontrol unit 101.

In accordance with estimation results of a channel state of the uplinkoutput from the channel estimating unit 105 (radio channel state), aresource assignment request from the mobile station apparatus 200,information of the PRB usable on each mobile station apparatus 200,scheduling information input from the higher layer 108, and the like,the scheduling unit 104 generates scheduling information during theuplink scheduling for use in a selection process of the uplink transportformat (a transmission form, such as assignment of the physical resourceblock, the modulation scheme, and the encoding scheme) for modulatingeach piece of data, and for use in uplink scheduling. The schedulinginformation for use in the uplink scheduling is output to the datacontrol unit 101.

The scheduling unit 104 maps the logical channel of the downlink inputfrom the higher layer 108 to the transport channel, and then outputs theresulting logical channel to the data control unit 101. Upon processingcontrol data acquired in the uplink and input from the data extractorunit 107 and the transport channel as appropriate, the scheduling unit104 maps the resulting data to the logical channel of the uplink andthen outputs the mapping result to the higher layer 108.

In order to demodulate the uplink data, the channel estimating unit 105estimates the channel state of the uplink from a demodulation referencesignal (DRS), and outputs the estimation result to the reception datademodulator unit 106. In order to schedule the uplink, the channelestimating unit 105 estimates the channel state of the uplink from thesounding reference signal (SRS), and outputs the estimation result tothe scheduling unit 104.

The reception data demodulator unit 106 also serves as an OFDMdemodulator unit and/or a DFT-Spread-OFDM (DFT-S-OFDM) demodulator unit,which demodulates reception data modulated in accordance with an OFDMscheme and/or SC-FDMA scheme. In accordance with the uplink channelstate estimation result input from the channel estimating unit 105, thereception data demodulator unit 106 performs, on the modulation datainput from the radio unit 103, signal processing comprising DFTconversion, subcarrier mapping, IFFT transform and filtering. Thereception data demodulator unit 106 thus performs a demodulationprocess, thereby outputting the demodulation result to the dataextractor unit 107.

The data extractor unit 107 verifies the data input from the receptiondata demodulator unit 106 as to whether the input data is in error ornot and outputs the verification result (ACK or NACK) to the schedulingunit 104. The data extractor unit 107 also separates the transportchannel and control data in the physical layer from the data input fromthe reception data demodulator unit 106, and outputs the separated datato the scheduling unit 104. The separated output data comprises CSI,CQI, PMI, and RI transmitted from the mobile station apparatus 200,information indicating ACK/NACK for the downlink transport block, andthe scheduling request.

The higher layer 108 performs processes in a packet data convergenceprotocol (PDCP) layer, a radio link control (RLC) layer, and a radioresource control (RRC) layer. In order to control processors in a lowerlayer in an integral fashion, the higher layer 108 comprises aninterface (not illustrated) between the higher layer 108 and each of thescheduling unit 104, the antenna 109, the radio unit 103, the channelestimating unit 105, the reception data demodulator unit 106, the datacontrol unit 101, the transmission data modulator unit 102 and the dataextractor unit 107.

The higher layer 108 manages configuration information in each type ofchannel notified a signal by the higher layer (such as RRC signaling),and on channel generation, the higher layer 108 notifies the processor(such as the data control unit 101 or the scheduling unit 104) in thelower layer of the configuration information.

The higher layer 108 comprises the radio resource control unit 110 (alsoreferred to a controller). The radio resource control unit 110 manages avariety of configuration information, manages system information,controls paging, manages the communication state of each mobile stationapparatus 200, manages the movement of handover, manages the bufferstate of each mobile station apparatus 200, manages the connectionconfiguration of unicast and multicast bearers, and manages a mobilestation identity (UEID). Also, the higher layer 108 receives informationfrom and transmits information to the base station apparatus 100, andthe higher node.

[Configuration of Mobile Station Apparatus 200]

FIG. 3 is a block diagram schematically illustrating the configurationof the mobile station apparatus 200 of the embodiment of the presentinvention. The mobile station apparatus 200 comprises a data controlunit 201, a transmission data modulator unit 202, a radio unit 203, ascheduling unit 204, a channel estimating unit 205, a reception datademodulator unit 206, a data extractor unit 207, a higher layer 208 andan antenna 209. The data control unit 201, the transmission datamodulator unit 202, the radio unit 203, the scheduling unit 204, thehigher layer 208 and the antenna 209 form a transmitter (mobile stationtransmitter), and the radio unit 203, the scheduling unit 204, thechannel estimating unit 205, the reception data demodulator unit 206,the data extractor unit 207, the higher layer 208, and the antenna 209form a receiver (mobile station receiver).

Processing of the uplink physical layer is performed by the data controlunit 201, the transmission data modulator unit 202 and the radio unit203. Processing of the downlink physical layer is performed by the radiounit 203, the channel estimating unit 205, the reception datademodulator unit 206 and the data extractor unit 207.

The data control unit 201 receives a transport channel from thescheduling unit 204. The data control unit 201 maps the transportchannel and a signal and a channel generated in the physical layer to aphysical channel in accordance with scheduling information input fromthe scheduling unit 204. Each piece of data thus mapped is output to thetransmission data modulator unit 202.

The transmission data modulator unit 202 modulates transmission data inaccordance with the OFDM scheme and/or the SC-FDMA scheme. Thetransmission data modulator unit 202 performs on data input from thedata control unit 201 signal processing comprising data modulation, DFT(discrete Fourier transform) process, subcarrier mapping, IFFT (inversefast Fourier transform) process, CP insertion, and filtering. Thetransmission data modulator unit 202 thus generates transmission dataand outputs the generated transmission data to the radio unit 203.

The radio unit 203 up-converts modulated data input from thetransmission data modulator unit 202 into a signal on a radio frequency,thereby generating a radio signal. The radio unit 203 transmits theradio signal to the base station apparatus 100 via the antenna 209.Also, the radio unit 203 receives via the antenna 209 a radio signalmodulated with downlink data from the base station apparatus 100,down-converts the radio signal into a baseband signal, and then outputsresulting received data to the channel estimating unit 205 and thereception data demodulator unit 206.

The scheduling unit 204 performs a process in the medium access control(MAC) layer. The scheduling unit 204 performs mapping on a logicalchannel and a transport channel, and scheduling (comprising HARQprocess, and selection of transport format). In order to controlprocessors in the physical layer, the scheduling unit 204 comprises aninterface (not illustrated) between the scheduling unit 204 and each ofthe antenna 209, the data control unit 201, the transmission datamodulator unit 202, the channel estimating unit 205, the reception datademodulator unit 206, the data extractor unit 207 and the radio unit203.

In accordance with scheduling information from the base stationapparatus 100 or the higher layer 208 (transport format and HARQretransmission information), the scheduling unit 204 generates, duringdownlink scheduling, scheduling information for use in reception controlof the transport channel, a physical signal, and a physical channel, andfor use in HARQ retransmission control and downlink scheduling. Thescheduling information for use in the downlink scheduling is output tothe data control unit 201.

In accordance with the buffer state of the uplink input from the higherlayer 208, scheduling information (a transport format, HARQretransmission information, and the like) of the uplink from the basestation apparatus 100 input from the data extractor unit 207, schedulinginformation input from the higher layer 208 and the like, the schedulingunit 204 generates, during scheduling of the uplink, schedulinginformation for use in a scheduling process to map the logical channelof the uplink input from the higher layer 208 to the transport channel,and for use in scheduling of the uplink. The transport format of theuplink is derived from information notified by the base stationapparatus 100. These pieces of scheduling information are output to thedata control unit 201.

The scheduling unit 204 maps the logical channel of the uplink inputfrom the higher layer 208 to the transport channel, and then outputs theresulting mapped data to the data control unit 201. The scheduling unit204 also outputs, to the data control unit 201, CSI, CQI, PMI, and RIinput from the channel estimating unit 205, and verification results ofa CRC check input from the data extractor unit 207. Upon processingcontrol data acquired in the downlink and input from the data extractorunit 207 and the transport channel as appropriate, the scheduling unit204 maps the resulting data to the logical channel of the downlink andthen outputs the mapping result to the higher layer 208.

In order to demodulate the downlink data, the channel estimating unit205 estimates the channel state of the downlink from a demodulationreference signal, and outputs the estimation result to the receptiondata demodulator unit 206. The channel estimating unit 205 notifies thebase station apparatus 100 of estimation results of the channel state ofthe downlink (radio channel state, CSI, CQI, PMI, and RI). To this end,The channel estimating unit 205 estimates the channel state of thedownlink from the downlink reference signal, and then outputs to thescheduling unit 204 the estimation results as CSI, CQI, PMI, and RI.

The reception data demodulator unit 206 demodulates reception datamodulated in accordance with the OFDM scheme. In accordance with thechannel state estimation results of the downlink input from the channelestimating unit 205, the reception data demodulator unit 206 demodulatesmodulation data input from the radio unit 203 and outputs thedemodulated data to the data extractor unit 207.

The data extractor unit 207 performs a CRC check on data input from thereception data demodulator unit 206 to determine whether the input datais in error or not, and outputs the verification results (informationindicating ACK or NACK) to the scheduling unit 204. The data extractorunit 207 separates the transport channel and control data in thephysical layer from the data input from the reception data demodulatorunit 206, and then outputs the separated data to the scheduling unit204. The separated control data comprises scheduling information, suchas the resource assignment of the downlink or the uplink, and HARQcontrol information of the uplink.

The higher layer 208 performs processes in a packet data convergenceprotocol (PDCP) layer, a radio link control (RLC) layer, and a radioresource control (RRC) layer. In order to control processors in thelower layer in an integral fashion, the higher layer 208 comprises aninterface (not illustrated) between the higher layer 208 and each of thescheduling unit 204, the antenna 209, the data control unit 201, thetransmission data modulator unit 202, the channel estimating unit 205,the reception data demodulator unit 206, the data extractor unit 207 andthe radio unit 203.

The higher layer 208 manages configuration information corresponding toeach type of channel notified a signal in a higher layer (such as RRCsignaling), and on channel generation, the higher layer 208 notifies theprocessor (such as the data control unit 201 or the scheduling unit 204)in the lower layer of the configuration information.

The higher layer 208 comprises the radio resource control unit 210 (alsoreferred to a controller). The radio resource control unit 210 manages avariety of configuration information, manages system information,controls paging, manages the communication state of the mobile stationapparatus 200, manages the movement of handover, manages the bufferstate, manages connection configuration of unicast and multicastbearers, and manages a mobile station identity (also referred to UEID).

First Embodiment

A first embodiment of the communication system comprising the basestation apparatus 100 and the mobile station apparatus 200 is describedbelow. In the first embodiment, the base station apparatus 100 notifiesthe mobile station apparatus 200 of the DCI format. The DCI formatcomprises resource allocation information as to whether to allocate DMRSin localized resource allocation or distributed resource allocation, andinformation on a frequency offset of the DMRS. The frequency offset ofthe DMRS is a mobile station apparatus specific parameter (or a UEspecific parameter). If distributed resource allocation is enabled basedon the resource allocation information transmitted using the DCI format,the mobile station apparatus 200 determines the DMRS resource allocationusing the frequency offset of the DMRS. The DCI format comprisinginformation as to the availability of frequency offset hopping for theDMRS may be notified to the mobile station apparatus 200. If thefrequency offset hopping for the DMRS is configured to be possible inthe DCI format, the mobile station apparatus 200 determines a frequencyoffset pattern responsive to a slot number, determines the resourceallocation for the DMRS in accordance with the frequency offset and thefrequency offset hopping pattern, and then transmits the generated DMRSto the base station apparatus 100. The frequency offset hopping patternis a cell specific parameter (or a base station apparatus specificparameter). Information indicating the availability of the frequencyoffset hopping for the DMRS may be notified using the RRC signaling.

The frequency offset hopping pattern n^(cell) _(hop) may be determinedusing a pseudo-random sequence based on a slot number n_(s). Thefrequency offset hopping pattern n^(cell) _(hop) is a cell specificparameter (or a base station apparatus specific parameter). For example,the mobile station apparatus 200 may determine the frequency offsethopping pattern n^(cell) _(hop) in accordance with Equation (1).

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 1} \right\rbrack & \; \\{{n_{hop}^{cell}\left( n_{s} \right)} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu} {comb}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {disabled}} \\{\sum\limits_{i = 0}^{7}{{c\left( {{8n_{s}} + i} \right)} \cdot 2^{i}}} & {{if}\mspace{14mu} {comb}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {enabled}}\end{matrix} \right.} & (1)\end{matrix}$

In Equation (1), c(i) represents a pseudo-random sequence. Thepseudo-random sequence is defined by a 31 sequence length of Goldsequence. An output sequence c(n) (n=0, 1, . . . , M_(PN)−1) of asequence length M_(PN) is defined by Equation (1A).

[Equation 1A]

c(n)=(x ₁(n+N _(C))+x ₂(n+N _(C)))mod 2  (1A)

In Equation (1A), Nc=1600. A first m sequence x₁ is initialized withx₁(0)=1, x₁(n)=0 (n=1, 2, . . . , 30). An initial value of a second msequence x₂(n) (n=0, 1, 2, . . . , 30) is defined by Equation (1B).

[Equation 1B]

c _(init)=·Σ_(i=0) ³⁰ x ₂(i)·2^(i)   (1B)

An initial value of x₂ is determined by determining an initial valuec_(init) of a pseudo-random sequence generator defined by a signalsequence of each physical channel. The mobile station apparatus 200determines values of x₁ and x₂ with the value of n being 31 or higher inaccordance with Equation (1C).

[Equation 1C]

x ₁(n+31)=(x ₁(n+3)+x ₁(n))mod 2

x ₂(n+31)=(x ₂(n+3)+x ₂(n+2)+x ₂(n+1)+x ₂(n))mod 2  (1C)

In this case, the initial value c_(init) being used for thepseudo-random sequence generator used to generate the pseudo-randomsequence is determined using a physical layer cell identity N^(cell)_(ID) For example, the mobile station apparatus 200 may determine theinitial value c_(init) being used for the pseudo-random sequencegenerator in accordance with Equation (2). More specifically, if thephysical layer cell identity is notified by the base station apparatus100, the mobile station apparatus 200 may determine the initial valuec_(init) being used for the pseudo-random sequence generator on thebasis of the physical layer cell identity.

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} 2} \right\rbrack & \; \\{c_{init} = \left\lfloor \frac{n_{ID}^{cell}}{n_{PRF}^{DMRS}} \right\rfloor} & (2)\end{matrix}$

Note that the initial value c_(init) being used for the pseudo-randomsequence generator may be determined on the basis of a virtual cellidentity in a case that the mobile station apparatus 200 is notified ofthe virtual cell identity. The initial value c_(init) being used for thepseudo-random sequence generator may be determined on the basis of acommon identity among coordinated cells in a case that the mobilestation apparatus 200 is notified of the common identity. The commonidentity may be different from a physical cell identity. Theseidentities may be specifically determined in the system. Theseidentities may be notified to the entire cell. These identities may benotified to the mobile station apparatus 200 by the base stationapparatus 100 in an individual basis. If the mobile station apparatus200 is notified of at least one of the identities by the base stationapparatus 100, the mobile station apparatus 200 may determine theinitial value c_(init) of the pseudo-random sequence generator on thebasis of any one of the one or more notified identities.

The mobile station apparatus 200 may further determine a frequencydomain starting position n^(SC) _(offset) of subcarrier (resourceelement) mapping of the DMRS on the basis of a frequency offset n^(UE)_(offset) and a offset hopping pattern n^(cell) _(hop), which thefrequency offset n^(UE) _(offset) is a mobile station apparatus specificparameter, and which the offset hopping pattern n^(cell) _(hop) is acell specific parameter. Also, n^(SC) _(offset) may be a frequencyoffset of the subcarrier(s) comprising the DMRS in the resource block.For example, the mobile station apparatus 200 determines the frequencyoffset n^(SC) _(offset) of the subcarrier(s) in accordance with Equation(3).

[Equation (3)]

n _(offset) ^(SC)=(n _(offset) ^(UE) +n _(hop) ^(cell)(n _(s)))mod n_(RRF) ^(DMRS)  (3)

Note that the offset hopping pattern n^(cell) _(hop) being a cellspecific parameter may be determined on the basis of a pseudo-randomsequence comprising a slot number and a physical layer cell identity.For example, the mobile station apparatus 200 may determine the offsethopping pattern n^(cell) _(hop) in accordance with Equation (4).

$\begin{matrix}{\mspace{79mu} \left\lbrack {{Equation}\mspace{14mu} 4} \right\rbrack} & \; \\{{n_{hop}^{cell}\left( {n_{s},N_{ID}^{cell}} \right)} = \left\{ \begin{matrix}0 & {{if}\mspace{14mu} {comb}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {disabled}} \\{\sum\limits_{i = 0}^{7}{{c\left( {{8n_{s}} + {8N_{ID}^{cell}} + i} \right)} \cdot 2^{i}}} & {{if}\mspace{14mu} {comb}\mspace{14mu} {hopping}\mspace{14mu} {is}\mspace{14mu} {enabled}}\end{matrix} \right.} & (4)\end{matrix}$

FIG. 4A and FIG. 4B illustrate configuration examples of DMRS resourceallocation of the first embodiment of the present invention. FIG. 4A isa resource allocation chart in a case in which localized resourceallocation is enabled based on resource allocation information for theDMRS notified by the base station apparatus 100. The resource allocationremains the same as related art resource allocation. FIG. 4B is aresource allocation chart in a case in which distributed resourceallocation is enabled based on resource allocation information for theDMRS notified by the base station apparatus 100 dictates. In a case thatthe resource allocation with the distributed resource allocation isenabled, subcarriers are allocated at constant intervals (samesubcarrier spacing) to keep PAPR low (this allocation may also bereferred to as a comb spectrum allocation). The base station apparatus100 notifies the mobile station apparatus 200 information (repetitionfactor) that indicates the number of subcarrier intervals (subcarrierspacings) at which DMRS is allocated. The frequency domain startingposition of the subcarrier(s) (resource element(s)) mapping of the DMRSis determined by the frequency offset n^(SC) _(offset) calculated inaccordance with Equation (3).

FIG. 5 illustrates an example of DMRS distributed resource allocation ofthe first embodiment of the present invention. One resource block hereincomprises 12 subcarriers (resource elements), for example. If theresource allocation is configured to be the distributed resourceallocation, the mobile station apparatus 200 may determine one or moresubcarriers at which the DMRS is assigned based on the distributedresource allocation, in accordance with a repetition factor n^(DMRS)_(RPF) indicating the number of subcarrier spacings at which the DMRS isassigned, and in accordance with the frequency offset n^(SC) _(offset)indicating the subcarrier at which the resource allocation starts. Therepetition factor n^(DMRS) _(RPF) may be specifically determined in thesystem. The repetition factor n^(DMRS) _(RPF) may be comprised inbroadcast information, and then the broadcast information is broadcastfrom the base station apparatus 100 to a plurality of mobile stationapparatuses 200. The repetition factor n^(DMRS) _(RPF) may be notifiedto the mobile station apparatus 200. In other words, the base stationapparatus 100 may configure the repetition factor n^(DMRS) _(RPF) to bespecific to the cell. The base station apparatus 100 may also configurethe repetition factor n^(DMRS) _(RPF) to be specific to the mobilestation apparatus.

FIG. 6 is a block diagram schematically illustrating a configuration ofthe scheduling unit 204 in the mobile station apparatus 200 of the firstembodiment of the present invention. The scheduling unit 204 is notifiedof DMRS configuration information related to one or more parameters forDMRS by the higher layer 208. The scheduling unit 204 outputs theconfiguration information to a DMRS resource allocation setter 2041. Inresponse to the input configuration information, the DMRS resourceallocation setter 2041 generates transmission data for the DMRS. Ifcontrol information from the data extractor unit 207 comprisesinformation indicating the distributed resource allocation for the DMRS,a DMRS frequency offset determiner 2042 determines a frequency offsetvalue for the DMRS in distributed resource allocation, and in responseto the frequency offset value, the DMRS resource allocation setter 2041determines the resource allocation for the DMRS. More specifically, theDMRS resource allocation setter 2041 determines the frequency domainstarting position of the DMRS subcarrier (resource element) mapping. Thescheduling unit 204 outputs the transmission data as part of thescheduling information to the data control unit 201.

The resource allocation information may be 1-bit information. Morespecifically, the resource allocation information may be only 1-bitinformation indicating whether the resource allocation information isthe localized resource allocation or the distributed resourceallocation. The repetition factor may be specifically determined in thesystem. The repetition factor may be comprised in the broadcastinformation, and the broadcast information may be broadcast from thebase station apparatus 100 to the plurality of mobile stationapparatuses 200. The repetition factor may be individually notified fromthe base station apparatus 100 to the mobile station apparatus 200.

The resource allocation information may be 2-bit information. If theresource allocation information is indicated by the 2-bit information, aDMRS repetition factor index (DMRS RPF index) may be associated with thevalue of the repetition factor n^(DMRS) _(RPF) as listed in Table 1.More specifically, the 2-bit information and four types of repetitionfactor values may be associated with each other. If the DMRS repetitionfactor index is indicated by 3-bit information, the 3-bit informationmay be associated with eight types of repetition factor values. Ifn^(DMRS) _(RPF)=1, the mobile station apparatus 200 configures the DMRSresource allocation to be the localized resource allocation. Morespecifically, if n^(DMRS) _(RPF)=1, the mobile station apparatus 200does not perform the distributed resource allocation. The resourceallocation information may be information in two bits or more.

TABLE 1 DMRS RPF index n^(DMRS) _(RPF) 0 1 1 2 2 3 3 4

A transmission bandwidth of the DMRS is the same regardless of thelocalized resource allocation or the distributed resource allocation. Ifthe subcarrier spacing is widened, the number of subcarriers used totransmit the DMRS is reduced accordingly in a case of the samebandwidth. For this reason, the uplink reference signal sequence lengthchanges in response to a change in the number of subcarriers.

FIG. 7 illustrates a configuration example of a control informationfield comprised in the DCI format. FIG. 7A illustrates the configurationof a DCI format A when the distributed resource allocation is disabledbased on the resource allocation information for the DMRS comprised in aUE capability of the mobile station apparatus 200. For example, usingRRC signaling, the mobile station apparatus 200 notifies the basestation apparatus 100 of information indicating an availability ofwhether the distributed resource allocation can be performed or not inthe resource allocation for the DMRS. For example, the mobile stationapparatus 200 notifies the base station apparatus 100 of the informationindicating as the UE capability the availability of whether thedistributed resource allocation can be performed or not.

For example, the DCI format A is used when the base station apparatus100 performs the scheduling operation on the PUSCH. More specifically,the DCI format A is used when the mobile station apparatus 200 performstransmission in the PUSCH on one transmit port. The DCI format A is alsoused when the mobile station apparatus 200 performs transmission in thePUSCH on two transmit ports (the number of transmit ports of two or moreis also acceptable).

For example, the information to be transmitted in the DCI format Acomprises information used to differentiate the DCI format A fromanother format (Flag for format differentiation), information to dictatetransmission involving hopping (Frequency hopping flag), resourceassignment information for the PUSCH (Resource block assignment),information indicating a modulation scheme, a coding rate, and aretransmission parameter (Modulation and Coding Scheme and redundancyversion), information to identify whether the transmission data is newdata (New data indicator), TPC command information for scheduled PUSCH(TPC command for scheduled PUSCH), information indicating a cyclic shiftand an orthogonal cover code (OCC) for a demodulation reference signal(Cyclic shift for DM RS and OCC index), transmission request informationof the CSI (CSI request), a padding bit (Padding bit or 0 padding), andtransmission request information of SRS that is configured in responseto a notification from the RRC signaling (SRS request).

Information fields mapped to these pieces of information are defined inthe DCI format A. More specifically, the DCI format A comprises uplinkscheduling information. The DCI format A comprises the uplink schedulinginformation of a given (particular) mobile station apparatus 200. Inother words, the DCI format A is arranged in a UE specific search space(USS) or a common search space (CSS).

FIG. 7B illustrates a DCI format B in a case in which the distributedresource allocation is enabled based on the resource allocationinformation for the DMRS comprised in the UE capability. Defined in theDCI format B are control information comprised in the DCI format A andinformation fields that are mapped to a resource allocation flag(Localized/Distributed resource allocation flag for DMRS) to switch theresource allocation for the DMRS (the localized resource allocation/thedistributed resource allocation). Also defined in the DCI format B is aninformation field mapped to a transmission comb index (DMRS transmissioncomb index) (hatched portion) as a frequency offset specific to themobile station apparatus 200 of the DMRS. A notification from the higherlayer may switch between the DCI format A and the DCI format B in whichthe information field that maps the resource allocation flag and/or thetransmission comb index is newly defined. In response to a signal of thehigher layer transmitted from the base station apparatus 100, the mobilestation apparatus 200 switches between monitoring (attempting to decode)the DCI format A and monitoring (attempting to decode) the DCI format Bcomprising the resource allocation flag and/or the transmission combindex.

More preferably, the control information to be added to the DCI format Acomprises information indicating the availability of the frequencyoffset hopping for the DMRS (DMRS comb hopping flag) (shadowed portionin FIG. 7C). FIG. 7C illustrates the configuration of a DCI format Ccomprising information of the availability of the frequency offsethopping for the DMRS (DMRS comb hopping flag). Also defined in the DCIformat C is, in addition to the control information comprised in the DCIformat B, an information field that maps the availability of thefrequency offset hopping for the DMRS. Similarly, in response to asignal in the higher layer transmitted from the base station apparatus100, the mobile station apparatus 200 may switch between monitoring theDCI format A and monitoring (attempting to decode) the DCI format Ccomprising information indicating the resource allocation flag and/orthe transmission comb index and/or the information indicating theavailability of the frequency offset hopping.

FIG. 8A and FIG. 8B illustrate examples of frequency offset hopping ofDMRS of the first embodiment of the present invention. FIG. 8Aillustrates the example where the DMRS radio resources transmitted froma mobile station apparatus 200-1 in a cell #1 (UE200-1 of Cell #1) and amobile station apparatus 200-2 in a cell #2 (UE200-2 of Cell #2) overlapeach other between slots. In this case, since the DMRS transmitted fromthe mobile station apparatus 200-1 and the DMRS transmitted from themobile station apparatus 200-2 are allocated to the same resource,interference occurs between the DMRSs. The base station apparatus 100 inthe cell #1 may now perform channel estimation based on the DMRStransmitted from the mobile station apparatus 200-1. Since the DMRStransmitted from the mobile station apparatus 200-1 suffers frominterference from the DMRS transmitted from the mobile station apparatus200-2, channel estimation accuracy is substantially degraded. If theDMRS is used in the demodulation process of another signal,communication quality is difficult to ensure. If the hopping of thefrequency offset (Comb hopping) is enabled for the mobile stationapparatus 200-2 (FIG. 8B), the mobile station apparatus 200-2 and themobile station apparatus 200-1 transmit the DMRSs with different offsetsconfigured between slots. The mobile station apparatus 200-2 is thusfree from overlapping with the radio resource for the DMRS contiguouslytransmitted by the mobile station apparatus 200-1. Interference betweenthe DMRSs is reduced, and communication quality is maintained.

When the mobile station apparatus 200 performs the PUSCH transmissionwith the DMRS for the PUSCH on a plurality of transmit ports, the mobilestation apparatus 200 allocates the DMRS for the PUSCH to the samecarrier on each of the plurality of transmit ports. More specifically,the mobile station apparatus 200 configures the same frequency offsetand the same repetition factor on the plurality of transmit ports.

When the mobile station apparatus 200 performs the PUSCH transmissionwith the DMRS for the PUSCH on a plurality of transmit ports, the mobilestation apparatus 200 may allocate the DMRS for the PUSCH to subcarriersdifferent from transmit port to transmit port. More specifically, themobile station apparatus 200 may configure combinations different infrequency offset and repetition factor from transmit port to transmitport. For example, the DMRS is allocated to a first subcarrier ontransmit port #0 and transmit port #1, and the DMRS is allocated to asecond subcarrier different from the first subcarrier on transmit port#2 and transmit port #3. In this way, interference among a plurality ofDMRSs transmitted using a plurality of transmit ports of the mobilestation apparatus 200 is thus reduced.

Second Embodiment

A second embodiment of the communication system comprising the basestation apparatus 100 and the mobile station apparatus 200 is described.A general device configuration of the second embodiment remainsunchanged from that of the first embodiment, and the discussion thereofis omitted herein. In the second embodiment, the base station apparatus100 notifies the mobile station apparatus 200 of a DCI format comprisingresource allocation information for DMRS, a frequency offset, and afrequency offset shift pattern. The frequency offset and the frequencyoffset shift pattern are parameters being used for the DMRS distributedallocation, and the frequency offset is the mobile station apparatusspecific parameter and the frequency offset shift pattern is the cellspecific parameter. If the distributed resource allocation is enabledbased on the resource allocation information for the DMRS transmittedusing the DCI format, the mobile station apparatus 200 determines theDMRS resource allocation based on the frequency offset, the frequencyoffset shift pattern, and a slot number. The mobile station apparatus200 then transmits, to the base station apparatus 100, the DMRS based onthe DMRS resource allocation.

The frequency offset n^(SC) _(offset) of the subcarrier(s) in the DMRSdistributed resource allocation may be determined in accordance with afrequency offset n^(UE) _(offset) and a frequency offset shift patternΔ^(cell) _(shift) (Δ^(cell) _(shift)=0, 1, . . . , n^(DMRS) _(RPF)−1)and a slot number n_(s) using Equation (5). The frequency offset n^(UE)_(offset) is a mobile station apparatus parameter (or a UE specificparameter) and the frequency offset shift pattern Δ^(cell) _(shift) is acell specific parameter (or a base station apparatus parameter).

[Equation (5)]

n ^(SC) _(offset)(n _(s))=(n _(offset) ^(UE)+Δ_(shift) ^(cell) ·n_(s))mod n _(RPF) ^(DMRS)  (5)

The frequency offset shift pattern Δ^(cell) _(shift) may be notifiedusing the RRC signaling. The frequency offset shift pattern Δ^(cell)_(shift) does not necessarily have to be notified by the base stationapparatus 100. More specifically, the frequency offset shift patternΔ^(cell) _(shift) may be determined using a physical layer cellidentity. The frequency offset shift pattern Δ^(cell) shift may bedetermined using a virtual cell identity in a case that the mobilestation apparatus 200 is notified of the virtual cell identity.

The use of the frequency offset shift pattern Δ^(cell) _(shift)eliminates the need to dynamically notify the availability the frequencyoffset hopping or the frequency offset shift, and thus the need to addcorresponding information bit to the DCI format.

When the mobile station apparatus 200 performs the PUSCH transmissionwith the DMRS for the PUSCH using a plurality of transmit ports, themobile station apparatus 200 allocates the DMRS for the PUSCH to thesame subcarrier on each of the transmit ports. More specifically, themobile station apparatus 200 configures the same frequency offset andthe same repetition factor for the plurality of transmit ports.

When the mobile station apparatus 200 performs the PUSCH transmissionwith the DMRS for the PUSCH using a plurality of transmit ports in thesame subframe, the mobile station apparatus 200 may allocate the DMRSfor the PUSCH to subcarriers different from transmit port to transmitport. More specifically, the mobile station apparatus 200 may configurea combination different in frequency offset and repetition factor fromtransmit port to transmit port. For example, the mobile stationapparatus 200 allocates the DMRS to a first subcarrier on transmit port#0 and transmit port #1, and allocates the DMRS to a second subcarrierdifferent from the first subcarrier on transmit port #2 and transmitport #3. In this way, interference among a plurality of DMRSstransmitted using a plurality of transmit ports of the mobile stationapparatus 200 is thus reduced.

Third Embodiment

A third embodiment of the communication system comprising the basestation apparatus 100 and the mobile station apparatus 200 is described.A general device configuration of the third embodiment remains unchangedfrom that of the first embodiment, and the discussion thereof is omittedherein. In the third embodiment, the base station apparatus 100 notifiesthe mobile station apparatus 200 of a DCI format comprising resourceallocation information of DMRS, a frequency offset specific to themobile station apparatus in DMRS distributed resource allocation, andinformation indicating a cyclic shift (CS) performed on an uplinkdemodulation reference signal and an orthogonal cover code (OCC) (Cyclicshift for DM RS and OCC index). If the distributed resource allocationis enabled based on the resource allocation information for the DMRS inaccordance with the DCI format, the mobile station apparatus 200determines a frequency offset hopping pattern for the DMRS distributedresource allocation on each transmit port, using CS and OCC on eachtransmit port indicated by the information indicating the cyclic shift(CS) performed on the uplink demodulation reference signal and theorthogonal cover code (OCC).

For example, in accordance with Equation (6), the mobile stationapparatus 200 determines the frequency offset hopping pattern of thesubcarrier on each transmit port using a CS value n⁽²⁾ _(DMRS,λ) and anorthogonal cover code [w^((λ))(0), w^((λ))(1)] ([+1, +1] or [+1, −1])indicated by the information of the CS for DMRS and the OCC comprised inthe DCI format.

[Equation 6]

n _(offset,λ) ^(SC)(n _(s))=n _(offset) ^(UE) +w ^((λ))(n _(s) mod 2)·n_(DMRS,λ) ⁽²⁾)mod n _(RPF)  (6)

In accordance with the third embodiment, the frequency offset hoppingpattern is determined on each transmit port from the CS for the DMRS andthe OCC notified by the DCI format. This eliminates the need to notifythe frequency offset hopping pattern on each transmit port, and anamount of information that the base station apparatus 100 notifies tothe mobile station apparatus 200 is not increased.

More specifically, the mobile station apparatus 200 generates a DMRSsignal sequence (demodulation reference signal sequence) on the basis ofthe information on the CS for the DMRS and the OCC that the base stationapparatus 100 notifies using the DCI format, and transmits the generatedDMRS signal sequence based on the frequency offset hopping patterndetermined on the basis of the information indicating the CS for theDMRS and the OCC.

The frequency offset hopping pattern for the DMRS distributed resourceallocation on each transmit port may be associated with a CS valuen_(cs,λ), of the DMRS. For example, the frequency offset hopping patternfor the DMRS distributed resource allocation may be determined inaccordance with Equation (7).

[Equation (7)]

n _(offset,λ) ^(SC)(n _(s))(n _(offset) ^(UE) +n _(CS,λ))mod n _(RPF)^(DMRS)  (7)

The CS value n_(cs,λ) of the DMRS is determined in accordance withEquation (8).

[Equation (8)]

n _(cs,λ)(n _(DMRS) ⁽¹⁾ +n _(DMRS,λ) ⁽²⁾ +n _(PN)(n _(s)))mod 12  (8)

Here, n⁽¹⁾ _(DMRS) is a CS value of the DMRS associated with the cyclicshift notified using the RRC signaling. n_(PN)(n_(s)) is a value that isdetermined from a pseudo-random sequence in accordance with Equation(9).

[Equation (9)]

n _(PN)(n _(s))=Σ_(i=0) ⁷ c(8N _(symb) ^(UL) ·n _(s) +i)·2^(i)  (9)

The pseudo-random sequence generator is initialized with an initialvalue c_(init) at the beginning of each radio frame, where the initialvalue c_(init) is in accordance with Equation (10).

$\begin{matrix}\left\lbrack {{Equation}\mspace{14mu} (10)} \right\rbrack & \; \\{c_{init} = {{\left\lfloor \frac{N_{ID}^{cell}}{30} \right\rfloor \cdot 2^{5}} + f_{SS}^{PUSCH}}} & (10)\end{matrix}$

Here, f^(PUSCH) _(ss) is a sequence shift pattern for the PUSCH and themobile station apparatus 200 determines f^(PUSCH) _(ss) in accordancewith Equation (11).

[Equation (11)]

f _(ss) ^(PUSCH)=(f _(ss) ^(PUCCH)+Δ_(ss))mod 30  (11)

Δ_(ss)ε{0, 1, . . . , 29}

Δ_(ss) represents a parameter, the configuration of which is notifiedusing the RRC signaling. f^(PUCCH) _(ss) is a sequence shift pattern forthe PUCCH and the mobile station apparatus 200 determines f^(PUCCH)_(ss) in accordance with Equation (12).

[Equation 12]

f _(ss) ^(PUCCH) =N _(ID) ^(cell) mod 30  (12)

Using this method, the frequency offset pattern is thus determined inaccordance with a smaller amount of information.

More specifically, the base station apparatus 100 notifies the mobilestation apparatus 200 of a primary synchronization signal, a secondarysynchronization signal and a DCI format. The mobile station apparatus200 determines a physical layer cell identity from the primarysynchronization signal and the secondary synchronization signal,generates a DMRS signal sequence from the physical layer cell identityand information indicating CS for a DMRS and OCC transmitted using theDCI format, and transmits the DMRS signal sequence generated using afrequency offset hopping pattern on each transmit port determined inaccordance with the information indicating the CS for the DMRS and OCC.

If a connection is established between the base station apparatus 100and the mobile station apparatus 200, and carrier aggregation to beperformed using multiple carriers is possible, the mobile stationapparatus 200 configures, using the RRC signaling, a physical layer cellidentity for a carrier, the transmission of which is dictated by thebase station apparatus 100. The mobile station apparatus 200 generatesthe DMRS signal sequence based on the physical layer cell identitynotified using the RRC signaling and the information indicating the CSand OCC, and then transmits a DMRS signal sequence that has beengenerated in accordance with a frequency offset hopping pattern on eachtransmit port determined on the basis of the information indicating theCS for the DMRS and OCC.

The above-described embodiment is applicable to an integratedcircuit/chip set mounted on the base station apparatus 100 and themobile station apparatus 200. In the above-described embodiments, aprogram to implement the functions of the base station apparatus 100 andthe functions of the mobile station apparatus 200 may be recorded on acomputer-readable recording medium. A computer system may then read theprogram recorded on the recording medium, and execute the program toperform a control process of the base station apparatus 100 and themobile station apparatus 200. The term “computer system” comprises OSand hardware such as peripheral device.

The term “computer readable recording medium” refers to a portablemedium, such as a flexible disk, a magneto-optical disk, ROM, or CD-ROM,or a recording device, such as a hard disk, built into the computersystem. The “computer readable recording medium” may comprise acommunication line that holds dynamically the program for a short periodof time. The communication line transmits the program via acommunication channel such as a network like the Internet or acommunication line such as a telephone line. The “computer readablerecording medium” may also comprise a volatile memory in the computersystem that may be a server or a client and stores the program for apredetermined period of time. The program may implement part of theabove-described function. The part of the above-described function maybe used in combination with a program previously recorded on thecomputer system.

The embodiments of the present invention have been described in detailwith reference to the drawings. The specific configuration of theembodiments is not limited to the configuration described above. Avariety of designs is incorporated without departing from the scope ofthe present invention.

The present invention appropriately finds applications in the basestation apparatus 100, the mobile station apparatus 200, thecommunication system and the communication method.

REFERENCE SIGNS LIST

-   100 Base station apparatus-   101 Data control unit-   102 Transmission data modulator unit-   103 Wireless unit-   104 Scheduling unit-   105 Channel estimating unit-   106 Reception data demodulator unit-   107 Data extractor unit-   108 Higher layer-   109 Antenna-   110 Radio resource control unit-   200, 200-1, and 200-2 Mobile station apparatuses-   201 Data control unit-   202 Transmission data modulator unit-   203 Radio unit-   204 Scheduling unit-   205 Channel estimating unit-   206 Reception data demodulator unit-   207 Data extractor unit-   208 Higher layer-   209 Antenna-   210 Radio resource control unit

1. A terminal device comprising: a transmitter configured to transmit ademodulation reference signal associated with a physical channel; and areceiver configured to receive a configuration of comb of thedemodulation reference signal; wherein the transmitter is configured totransmit the demodulation reference signal mapped based on theconfiguration of comb.
 2. The terminal device according to claim 1,wherein the transmitter is configured to transmit the demodulationreference signal based on an orthogonal cover code, wherein a pattern ofthe orthogonal cover code is expanded in a case that the terminal deviceis configured with the comb of the demodulation reference signal.
 3. Abase station device comprising: a transmitter configured to transmit aconfiguration of comb of a demodulation reference signal related to aphysical channel.
 4. The base station device according to claim 3,wherein the transmitter is configured to transmit a configuration of anorthogonal cover code expand based on the configuration of the comb. 5.A transmitting method in a terminal device comprising: transmitting ademodulation reference signal associated with a physical channel; andreceiving a configuration of comb of the demodulation reference signal;wherein the demodulation reference signal is mapped based on theconfiguration of comb.